A conventional car silencer as shown in FIG. 1 includes: a connecting tube M connected to an engine exhaust manifold, an expansion pipe having expansion chamber C defined in the expansion pipe connected to the connecting tube M provided with several perforated partition plates P in the expansion chamber C for reducing sound waves from a car exhaust gas, and an exhaust pipe E connected to the expansion chamber C for discharging the waste gas from the car engine. However, such a conventional silencer does not provide any mechanism for absorbing or removing the pollutants laden in the exhaust gas, thereby causing serious air pollution problems to the environment.